Previous postmortem studies of people with severe forms of the disease showed that there was a decrease in a rare but important type of neuron in the dorsal striatum, deep within the brain. A team led by Christopher Pittenger, associate professor of psychiatry, investigated whether loss of those neurons could cause the symptoms.

They removed about half of these rare neurons (seen in red in accompanying image), which use the neurotransmitter acetylcholine, in the dorsal striatum of mice. These mice developed tic-like movements when they were stressed or exposed to amphetamine — two conditions that can bring out tics in patients, too.

However, other symptoms seen in Tourette syndrome, such as problems with motor skill learning and filtering sensory information, were not affected. This suggests that loss of these specific neurons may be sufficient to produce tics, but not other symptoms seen in Tourette syndrome, researchers say.